As the information society has developed and electronic devices have improved in performance, the improvements in signal transmission rate becomes more important in information communication devices. Optical transmission is a key technology for realizing such improvements in signal transmission rate.
Generally, an optical signal is transmitted as a single-ended optical signal. This single-ended optical signal is converted into a single-ended electrical signal on a receiver side, and is further converted into a differential signal by a single-ended input to differential output converting circuit. The latter conversion may cause asymmetry in differential signal, which hinders the improvement of signal transmission rate.